As circuit densities increase for next generation devices, the widths of interconnects, such as vias, trenches, contacts, gate structures and other features, as well as the dielectric materials therebetween, decrease to 22 nm or smaller dimensions, whereas the thickness of the dielectric layers remain substantially constant, with the result of increasing the aspect ratios of the features. Recently, complementary metal oxide semiconductor (CMOS) FinFET devices have been introduced into many logic and other applications and are integrated into various different types of semiconductor devices.
FinFET devices typically include semiconductor fins with high aspect ratios in which the channel and source/drain regions for the transistor are formed thereover. A gate electrode is then formed over and along side of a portion of the fin devices utilizing the advantage of the increased surface area of the channel and source/drain regions to produce faster, more reliable and better-controlled semiconductor transistor devices. Further advantages of FinFETs include reducing the short channel effect and providing higher current flow.
With the continuous scaling and architecture advancement, it has been a challenge to land the source/drain contact plug directly onto very narrow fins in the FinFET devices. Epitaxial layers have been used to increase the volume for better contact. The typical Si epitaxial film is faceted by {111} planes and has a diamond shape when it is observed along the transistor channel direction due to lower growth rate on <111> direction than <100> and <110> directions. The epitaxial film with dominant {111} facets may be disadvantageous because the lateral growth on the sidewall of the fin prohibits further distance reduction of neighboring fins. In addition, when the device has multi-fin FinFETs, voids can be formed in the merged source or drain due to the diamond shape.
Therefore, there is a need for an improved method to modify the growth rate for different crystal planes of epitaxial film in semiconductor devices.